Molecular markers

For the fingerprinting of plants

'The central dogma of life' has already been unravelled. The doublehelix structure of the DNA has answered many a question that dogged humanity for centuries and revolutionized many disciplines of scientific research. In fact, such is the nature of its revelation that the innovations it has led to never seem to cease. A short strand of DNA, the genetic blueprint of life, has cleared the haze from many medical and forensic science mysteries, initiated genetic engineering and gene therapy, and even made it possible to catalogue plant genetic resources.

Getting into genes

Molecular markers have brought to the fore an extremely efficient method of estimating the genetic diversity of germplasm collections of various plant species. They can enhance the speed and effectiveness of plant breeding, and can even be used for quality control. The process of mapping specific sites on the genome is termed as DNA or genetic marking. Genetic researchers at TERI have been working with plant DNA to estimate the total genetic diversity of some important plant species and authenticate the quality of tissue-cultured plants produced at TERI.

The big deal

Population explosion brings with it unwanted baggage of excess pressure on land (read deforestation and the near-loss of biodiversity) and on food resources (leading to hunger and malnutrition). Though such situations could best be countered by improvement in productivity and the quality of seasonal crops, most conventional technologies are extremely time-consuming and labourintensive. With an over 1500-fold variation in the genome size of all plant species, plant biotechnology seemed to have hit a roadblock. There was need for 'mole' sequences that would highlight the presence of genes of interest in the truly mind-boggling sequence of plant DNA.

The advent of the gene revolution

In vitro-raised clonal plantlets

Alive to the astounding opportunities promised by biotechnology, TERI, in 1985, set up its plant biotechnology group, which worked hard to get a firm grip on that elemental link to crop improvement and characterization, and conservation and, sustainable utilization of plant biodiversity. With this end in mind, scientists sought to devise DNA markers that would act as moles. These would pinpoint genes that control important desirable traits and provide clues to enhancing/improving the quantity/ quality of a particular plant. Molecular markers are also capable of signalling variations occurring at the DNA level, thereby making it possible to assess the genetic uniformity of tissue-cultured plants vis-à-vis the donor plant. Markers also invalidate all chances of mislabelling

of clones–a boon for plant breeding companies, forest departments, agricultural institutes, etc. The information laid out helps them select the best parental plants for generating hybrids or improved varieties, while ensuring optimal utilization of resources.

Beneficiaries

Molecular markers helped create a detailed map enabling plant breeders to indirectly select useful genes for replication via their association with neighbouring segments of marker DNA. This foolproof approach outdid the uncertainties of conventional breeding that relies on the physical appearance of a plant as the only criterion

of selection. Breeders in the country are harnessing the technology for early selection of desirable traits and to characterize plant species of national importance for conservation and better utilization.

The plant biotechnology group at TERI put the technology to test for validation and estimation of the amount of genetic diversity in pure strand and in mixed population germplasm collections of tea, mustard, rice, poplars, and medicinal plants like neem, amla, and ashwagandha. The group has established a catalogued databank of DNA fingerprinted profiles of mother material multiplied at TERI's MTP and other laboratories to ensure the clonal uniformity of tissuecultured plants. This databank has negated the possibility of any inadvertent use of duplicate mother plants resulting in micropropagation of monocultures or closely related genotypes.

Applications/benefits

Potential users of this technology can gain from a range of services being offered by the plant biotechnology group like gene cloning, DNA sequencing, molecular mapping and tagging of genes, and DNA fingerprinting besides analysis of genetic diversity. The use of DNA markers that are insensitive to environmental factors helps breeders screen individual plants at the seedling stage.

Though the cost of molecular marking is dependent on the nature of markers used, the type of material being processed, and the volume of work, the whole process works out to be cost-effective. Moreover, with smaller land/holdings and lower maintenance, the scoring time for identifying individuals with desired traits too gets greatly reduced.